Alkylation of aromatic hydrocarbons



April 10, 1945'. Q LlNN I "2,373,580

ALKYLATION OF ARoMAT Ic HYDROCARBONS Filed June 28, 1940' H IIINVENFOREobtained as a by-product of the to approximately 20 I Patented Apn'lo,

ICE:

2,313,580 I sum-non or AROMATIC n'rnaocannons 1 v Carl B. Linn, Chicago,111., assignor toUniversal Oil Products Company, Chicago, 111., acorporation of Delaware Application June 28, 1940, Serial No. 342,914

. 7 Claims.

This invention is concerned with the interaction of aromatichydrocarbons with alkyl fluorides ln'the presence of a catalyst. It ismore a relatively high conversion of specifically concerned with asimple and easily regulated, process involving the use of a liquidcatalyst which is altered only slightly in the course of the reactionbut which catalyzes the desired reactions with a. maximum of efficiency.

Processes for the formation of more highly 4 I alkylatedaromatichydrocarbons from less highly alkylated aromatic hydrocarbonsare of importance not "only from the standpoint of producing highantiknock motor fuel fractions but below the, surfaceof the hydrogenfluoride-arm for preparing 'alkylated aromatic hydrocarbons useful asintermediates in the production of syn-, thetic organic chemicals.

I In one speciflc embodiment the present inventloncomprises a processfor alkylati'ng aromatic hydrocarbons by alkylfluorides in the presenceof hydrogen fluoride to form alkylated aromatichydrocarbons.

According to the present inventionaromatic by providing a mixing zone,as a reactor containhydrocarbons, including benzene and its homologs,may be alkylated though obviously under somewhat modified conditions ofoperation when ,1 alkylating aromatic hydrocarbons of differentactivities and particularly when alkylating polycyclic aromatichydrocarbons. The alkyl fluoride utilized may be either normally gaseousor normally liquid such as ethyl fluorideand its higher boilinghomologs.

Alkyl fluorides used as alkylating agents in the process of'thisinvention may be formed by-the addition of hydrogenfluoride tomono-oleflnic hydrocarbons at a temperature within the approximate rangeof 60 to +100 0. and more preferably at a temperature of the order of to0 C. and under a pressure sufflcient to maintain in liquid phase a'substantial proportion of the. reaction mixture. .At the highertemperatures polymerization tends to occur which interferes with thedirect conversion of the original.

olefin into alkyl fluorides. .Such a formation of alkyl fluorides may bebrought about by the use 'of substantially anhydrous hydrogenfluoride'orby. employing a portion of the hydrogen fluoride boiling ,atabout 20,C.- and ac aromatic hydrocarbons and alkyl fluorides into alkylatedaromatic hydrocarbons. Also hydrogen fluoride formed from alkylfluorides during the alkylation reaction may subsequently be employed asalmay be utilized in the promatic hydrocarbon' mixture. In the batchopmoved and fractionatedto recover unchanged aromatics and the desiredalkylated products. Obviously the process may be made continuous ingbaflles and/or orifices, in which sufiicient time 'may be given forthe-completion of the desired alkylation reactions followed by asettling zone from which a hydrocarbon layer maybe withdrawn and;fractionated to recover desired a1- kylated hydrocarbons and unconvertedaromatics for recycling, while the lower layer of hydrogen fluoride maybe. pumped back to the alkylating step for further reaction.

The aforementioned reaction of an aromatic hydrocarbon with an alkylfluoride may-be carried out at'a temperature in the approximate range of-10 to +75 C. but preferably at a temperature of approximately 20 C.Pressure applied to the reaction mixture should preferably be sufficientto compensate for the vapor pressure of the reactants. Thus reaction maybe attained ride to contact in the liquid phase.

to advantage by subjecting a mixture of aromatic hydrocarbon, alkylfluoride, and hydrogen fluo- For the purpose of illustrating one type ofap,

paratus-in which the process may be conducted,

present aromatic anhydrous'hyd'rogen fluoride utiwhlch ls'cooled tomaintain temperatures below I this point or it can be used at highervtemperaparatus. matic hydrocarbon at all times and generally up timesthe molecular proportlon of alhl fluoride present, formation of olefinpolymers is avoided with the result that'thereis s'entially from theinvention, 7

the attached drawing shows diagrammatically in general side elevationandby the use of conventional figures an. arrangement of interconnectedunits suitable for continuous operations. It is understood that-minorfeatures of apparatus construction may be modified without departingesgenerally, broad scope of the Referring to the drawing an aromatichydrocarbon fractionrnay be introduced through line I containing valve 2to pump i which discharges through line 4 containing valve 5 whilehydrogen iiuoride'is introducedto line byway of'line 6 containing valve1 and pulnp 8 which discharges through line 9 and valve Ill. The mixtureof arcmatic hydrocarbon and hydrogen fluoride being conducted throughline- 4 is therein commingled with I u ted and continuous stream of anand valve l2 to pump alkyl fluoride or of an alkyl fluoride-aromatichydrocarbon mixture introduced through line H l3 which dischargesthrough line H and valve 15, to line 4, already mentioned, from whichthe commingled mixture passes through cooler it of any suitableconstruction and capacity for maintaining the temperature of reactionbelow any desired level while simultaneously permitting suflicient timeof contact for completion of the desired reactions.

" From cooler IS the reaction products follow line [1 containing valvel8 to separator 19 in which is. eflected a separation of hydrogenfluoride and hydrocarbons. The hydrogen fluoride layer is withdrawn fromseparator 19 through 'line 20 containing valve 2| to pump 22 whichdischarges through line 23 and valve 24 into line 4 so that the hydrogenfluoride catalyst may be recycled. If desired, a portion of the hydrogenfluoridebeing discharged by pump 22 through line 23 may be conductedtherefrom through line 26 and valve 21 to storage or to other use suchas the preparation of additional alkyl fluorides by reaction of hydrogenfluoride with a mono-olefin.

The hydrocarbon layer in the upper portion of separator l9 may be passedthrough line "and valve 29 to fractionator 30 containing reboiler coil3| and provided with vapor line 32 and valve 33 through which lowerboiling hydrocarbons may be released as an overhead fraction whilehigher boiling alkylated products may be withdrawn from the bottom offractionator 30 through line benzene with a major molecular proportionof ethyl fluoride. Hydrogen fluoride produced in the reaction may serveas additional catalyst in subsequent portions of the alkylation run.

The character of the process of the present invention and particularlyits commercial value are evident from the preceding specification andexample given, although neither section is intended to be undulylimiting in its generally an aromatic hydrocarbon which comprises sub-34 containing valve 35 to further cooling, not

shown, and to storage.

The unconverted lower boiling hydrocarbons passing through line 32 maybe conducted through condenser 36 and run-down line 31 containing valve38 to receiver 38 equipped with conventional gas releaseline 40containing valve 4| and with a liquid draw-off line 42 containing valve43 leading to pump 44 which discharges through line 45 containing valve46 to storage if desired, but ordinarily through line 25 containingvalve 41 and leading to line 4, already mentioned, to permit recyclingof unconverted aromatic hy- 'drocarbon and alkyl fluoride to furtheralkyla- .tion.

The exact temperature and pressure to be employed when alkylatingvarious aromatic hydrocarbons with various alkyl fluorides will dependupon the activity. and physical characteristics oi the reactantsinvolved so that best results will be obtained when conditions are firstdetermined on small scale apparatus. As a rule excessively elevatedtemperatures are neither necessary nor desirable and only suflicientpressure should be used to prevent excessive evaporation of ,thecatalyst or of thealkyl fluoride.

The following specific example is introduced as representative ofresults, obtainable by the process described, although with no intentionof .unduly limiting the generallybroad scope of the invention:

A mixture of 3 molecular proportions of benzene, 1 molecularproportionof ethyl fluoride, and

r 1 mol ular proportion of hydrogen fluoride amay be' contacted at 25 C.under a liquefying pressure to produce a mixture of mono-, di-, andpolyethyl benzenes dissolved in the excess of benzene contained in thecharge.

In general, mono-ethyl benzene may be obtained as a predominant productwhen charging a relatively high proportion of benzene while more highlyalkylated derivatives result from interaction of a smaller molecularproportion of jecting a molal excess of said aromatic hydrocarbon totreatment with an alkyl fluoride in the presence of hydrogen fluoride ata temperature between about -10 and about +75 C. under sufiicientpressure to maintain substantially liquid phase conditions.

4. A process for alkylating an aromatic hydrocarbon which comprisesintimately mixing said hydrocarbon with liquid hydrogen fluoride; in--hydrocarbon with liquid hydrogen fluoride; in-

troducing an alkyl fluoride to the mixture; maintaining the temperaturebetween about '-10 and about +75 C. while under a pressure sufllcient toinsure substantially liquid phase conditions; separating products of thereaction into unconverted aromatic hydrocarbon and alkyl fluoride,alkylated products, and hydrogen fluoride; and returning unconvertedaromatic hydrocarbon, alkyl fluoride, and hydrogen fluoride to furtherreaction. l

(i A process for'allrylating benzene which comprises intimately mixingsaid benzene with liquid hydrogen fluoride; introducing an alkylfluoride to the mixture; maintaining the temperature be tween about 10and about C. while under a pressure sufficient to insure substantiallyliquid phase conditions; separating products of the reaction into alkylbenzenes and unconverted benzene, alkyl fluoride, and hydrogen fluoride;and returning unconverted benzene, alkyl fluoride, and hydrogen fluorideto further reaction.

' 7. A process for producing ethyl ben'zenes which comprises subjectinga molal excess of benzene to treatment with ethyl fluoride inthepresence of hydrogen fluoride at a temperature between about -10 andabout +75 C. under sufficient pressure to maintain substantially liquid7 zene, ethyl fluoride, and-hydrogen fluoride; and

returning unconverted benzene, ethyl fluoride,

/and hydrogen fluoride to further reaction. 75,

carat B. mm.

